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I have encountered a weird problem: as far as I know, cache can be cleared by recycling the application pool.

However, in a recent project, cache is not cleared in that way. Instead we had to reset IIS to clear the cache.

What are the differences between these actions, and what might be the cause of the differences I've experienced?

Pooven
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D.J
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  • I found this reply rather useful: http://serverfault.com/a/474940/257995. Similar to the other answers here, but it also included the refresh option. – Pooven May 19 '15 at 19:44

2 Answers2

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When you recycle the AppPool, there is some overlap time. Your unhealthy worker process is marked for recycling, but continues to handle requests that it has already received. (It will not handle new requests). The unhealthy worker will be terminated once all its existing requests are handled.

With IIS reset, all workers are terminated and the cache in memory is cleared. New workers will be created once new requests come in.

So I think that for both an AppPool recycle and an IIS reset will clear the cache. As for as I know, that cache is stored in the Application domain. Once the unhealthy worker process terminates, all cache items should be destroyed.

Michael
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Pongsathon.keng
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  • Dose it means if we wait long enough and hit the page in a later time, the cache would be gone and cleared by recycle the application pool? – D.J Nov 23 '11 at 04:56
  • not working, i recycle a pool and check new pool and there are requests pending for more than 13 sec. IIS 7.5 windows server – Adeem Jun 17 '17 at 13:27
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Please check the following article for detailed explanation: http://fullsocrates.wordpress.com/2012/07/25/iisreset-vs-recycling-application-pools/

In short:

Recycling AppPool feature was introduced in IIS6.

IISRESET stops and starts all IIS related services. It tries to shutdown all components normally i.e. it sends request to shut down and waits for services to shutdown. It waits for all services to shutdown and then starts them back again.

AppPool recycle invokes a new worker process first, and then shutdown the old worker process. This makes the downtime lesser than IISRESET.

Pal R
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